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11.
Fe-modified ZSM-5 zeolites (Si/Al = 25) were prepared by adopting the liquid ion-exchange method with nitrate and oxalate of iron as Fe precursors and their catalytic performance was studied in the N2O decomposition reaction. The results of FT-IR and H2-TPR investigations indicated that (i) part of the iron ions could replace Brönsted acid protons at the straight channel wall (α sites), intersection of straight and sinusoidal channels (β sites), and sinusoidal channel wall (γ sites) within the ZSM-5 zeolite; and (ii) different Fe precursors gave rise to various distributions of α, β, and γ sites. We observed that the Fe-ZSM-5 catalyst prepared with iron oxalate as Fe precursor outperformed the ones prepared with iron nitrate as Fe precursor in the direct decomposition of N2O. Furthermore, the catalytic activity of iron ions located at the α sites was higher than those of iron ions located at the β and γ sites. 相似文献
12.
Vinyl bromides 2a-f, useful intermediates in organic synthesis, have been obtained under mild conditions and in good yields via electrochemical reduction of 1,1-dibromoalkenes 1a-f (readily available substrates). The reduction has been carried out in MeCN-tetraethylammonium perchlorate (TEAP) solutions, in the presence of a proton donor, at a Au, Hg, C or Ag cathode. The use of specific reducing agents, catalysts and bases, employed in the classical procedures, has been avoided. The isomeric E/Z ratio in vinyl bromides 2a-f is affected by the cathode material. 相似文献
13.
Qingjun Zhu Junko N. Kondo Satoshi Inagaki Takashi Tatsumi 《Topics in Catalysis》2009,52(9):1272-1280
Aluminosilicate H/CHA and H/MTF zeolites show remarkably different catalytic activities in the methanol and ethanol transformations
although they have similar pore size of 8-membered ring structures. Moreover, the produced ethylene is further converted on
H/CHA, but H/MTF is not active for the ethylene transformation. The correlations between the distinct catalytic differences
and their intrinsic structural properties, including topology and acidity, are discussed. 相似文献
14.
Simultaneous temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA) measurements were performed with n-propylamine and isopropylamine in H-FER and H-TON in order to test whether the Brønsted-acid sites associated with the 10-ring, straight channels in H-FER could be distinguished from the acid sites in the side cavities. In H-TON, the saturation uptakes were identical for both amines, as were the acid-site densities determined from the amounts of amine which reacted to olefin and ammonia products above 600 K. By contrast, the saturation uptake for isopropylamine in H-FER was much lower than the uptake of n-propylamine and the site density determined from the amounts which react were also significantly lower. It is argued that the n-propylamine results for H-FER provide a measure of the total Brønsted-acid-site density, while the isopropylamine results provide a measure of the site density in the 10-ring channels. 相似文献
15.
运用量子化学B3LYP方法,在6-311++g( d,p)基组水平上研究Br自由基和CH3 ONO的反应机理,优化得到了反应途径上反应物、过渡态和产物的几何构型;在B3LYP/6-311++g( d,p)优化的构型基础上,以CPCM模型得到了其在水溶液中各点的能量。研究结果表明:Br自由基与CH3 ONO有3种反应机制。第1种是Br自由基加成到CH3 ONO分子C原子上消除NO2的机制,第2种是Br自由基加成到CH3 ONO分子甲氧基O原子上消除NO的加成-消除机制,第3种是Br自由基对H直接夺取的机制。 相似文献
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TS-1, Ti-beta and Ti-MCM-41 molecular sieves have been prepared by direct hydrothermal synthesis method and applied to the epoxidation of n-hexene and cyclohexene with H2O2 under mild conditions. Ti-beta with extremely low Al content was synthesized by using a seed method to suppress the formation of diol produced by Brønsted acid sites present in Ti-beta. It was also found that a large amount of by-products (1-ol and 1-one) formed over hydrophilic Ti-MCM-41. We further modified Ti-MCM-41 by silylation with bis(trimethylsilyl) trifluoroacetamide (BSTFA). Among these catalysts, the Ti-beta with low content of Al enhanced the yield of epoxide and suppressed the formation of diol markedly. The silylated Ti-MCM-41 reduced the formation of by-products and promoted the yields of epoxide significantly. Based on experimental results, a reaction mechanism with two parallel and competitive reactions was proposed. 相似文献
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